Electrical connector

ABSTRACT

The present invention provides an electrical connector for connecting a core of a machine cable ( 37 ) to a pin ( 28 ) or a socket ( 32 ) of an electrical connection device. The connector has a first part and a second part. The first and second parts have first and second locking surfaces respectively and first and second separate contact surfaces ( 50, 52 ). The second part further includes a projection for securing the core of the machine cable and which is electrically connected to the second contact surface. The contact surfaces are so arranged that when the locking surfaces are interlocked, the contact surfaces are in electrical contact with each other so that an electrical contact is established between the core of the machine cable and the pin or socket.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of International Application No.PCT/AU2004/000065, filed 20 Jan. 2004 which claims the benefit ofAustralian Application No. 2003900291, filed 20 Jan. 2003 and AustralianApplication No. 2003902257, filed 9 May 2003, the disclosures of whichare hereby incorporated herein in their entireties by reference.

FIELD OF THE INVENTION

The present invention broadly relates to an electrical connector forconnecting a core of a machine cable to a pin or a socket of anelectrical connection device. Throughout this specification the term“machine cable” is used for any machine, reeling or trailing cable thatis arranged for delivery of power to mobile machinery such as largemachinery in petroleum or mining industry. The term “connector” is usedfor any connector including a plug, lug, electrical adaptor, coupler orreceptacle.

BACKGROUND OF THE INVENTION

Machine cables are typically used to provide an electrical connectionfor mobile electrical machines. For example, in the mining or petroleumindustry often large electrical machinery is used and each machine cablemay have to provide power in the order of a few hundred kilowatts.Typically such power is delivered with a voltage of one or morekilovolts. The cables usually comprise a plurality of cores and areconnected using connectors having sockets and pins.

FIG. 1 shows a cross-sectional representation of an electrical connectorfor connecting a socket with a core of such a machine cable. The Figureshows the socket 10 arranged to receive a pin (not shown). The Figurealso shows a thimble 12 which has an open end-portion 13 arranged toreceive the core of the machine cable. Fingers of the socket 10 arebiased by spring 15 so that an electrical connection with the pin may beachieved. However, the biasing force of the spring 15 may decay overtime and it may be necessary to replace the spring 15 and/or the socket10 from time to time. For this purpose the socket is realisableconnected to the thimble 12. The thimble 12 has a threaded portion 14and the socket 10 has a bore 16. The threaded portion 14 and the bore 16are arranged to receive stainless steel screw 18 which engages socket 10and thimble 12 via intermediate part 11. To reduce the likelihood thatthe stainless steel screw 18 may loosen over time, the stainless steelscrew 18 is inserted with a spring washer 19. Socket 10 and thimble 12have matching conical contact surfaces that match those of intermediatepart 11.

FIG. 2 shows a variation of the connector shown in FIG. 1. In this casecontact surfaces of socket 20 and thimble 22 do not match when thedevice is dissembled. However, when the stainless screw 18 is insertedinto the bore 24 of the socket 20 and received by the threaded portion26 of the thimble 22, the contact surface of the socket 20 bents thecontact surface of the thimble 22 outwards.

Both prior art devices have the disadvantage that the screw has to berelatively small as the screw head is positioned within the socket.However, the relatively small screw often does not provide sufficientstrength for the connection of the socket with the thimble. Further, thecontact surfaces are relatively small and the additional pathway that isprovided for the current through the screw itself is often notsatisfactory. The current has to pass through up to three interfaces(between socket, intermediate part and thimble or, alternatively,between socket and spring washer, between spring washer and screw headand between the thread of the screw and the thread of the bore) andcontact potentials, corrosion and contamination may result in contactresistivity at every interface. Further, the screw and the spring washerthemselves may not have satisfying electrical properties.

SUMMARY OF THE INVENTION

The present invention provides an electrical connector arranged forconnecting a core of a machine cable to a pin or a socket of anelectrical connection device, the connector comprising:

a first part having a first locking surface and having a further surfacethat forms a first contact surface, the first part further including apin or a socket which is electrically connected to the first contactsurface,

a second part having a second locking surface arranged to interlock withthe first locking surface and having a further surface that forms asecond contact surface which is arranged to contact the first contactsurface, the second part further including a projection for securing thecore of the machine cable to the second part, the projection beingelectrically connected to the second contact surface,

wherein the contact surfaces are arranged so that, when the lockingsurfaces are interlocked, the contact surfaces are in electrical contactwith each other so that an electrical contact is established between thecore of the machine cable and the pin or socket.

An advantage of the present invention is that the first part and thesecond part can be held together without any additional part which makesthe assemblement of the device relatively easy. Further, the assembleddevice may only have one interface which is of advantage for electricalproperties of the device. Prior art devices typically use a stainlesssteel screw which is inserted through bores of the socket and thethimble to hold together the thimble and the socket (see FIG. 1). Suchscrews are of relatively low electrically conductivity and their usagetherefore increases the electrical resistivity for current conductedthrough the conductor. The above-defined connector does not require sucha screw and consequently the cross-sectional area through whichelectricity can be conducted with a relatively low specific resistancemay be increased compared with prior art devices.

The electrical connection device typically is arranged for delivery of apower of a few hundred kilowatts. Further, the electrical connectiondevice typically is arranged for delivery of power having an associatedvoltage of one or more kilovolts.

The first locking surface typically is positioned between the firstcontact surface and the pin or socket.

The second contact surface typically is positioned between the secondlocking surface and the projection.

The first part may have opposing first and second end-portions, thefirst end-portion may include a socket and the second end-portions mayinclude the first contact surface.

Alternatively, the first end-portion may include a pin. The secondend-portion of the second part may include the second locking surfaceand the second end-portion of the first part may include the firstlocking surface.

At least one of the first part and the second part may be integrallyformed and typically both the first part and the second part are eachintegrally formed.

In one embodiment the first locking surface comprises a first threadedportion and the second locking surface comprises a second threadedportion arranged to receive the first threaded portion.

For example, the first threaded portion may be a cylindrical portionhaving an outer thread and the second threaded portion may be acomplimentary threaded bore arranged to receive the cylindrical portion.

Alternatively, the second threaded portion may be a cylindrical portionhaving an outer thread and the first threaded portion is a complimentarythreaded bore arranged to receive the cylindrical portion.

An advantage of this arrangement is that the threaded cylindricalportion and the respective threaded bore may be larger in diameter andconsequently mechanically and electrically stronger than those of priorart devices as there is no need to locate a screw and screw head withinanother part which is a requirement in the prior art (prior art devicesare shown in FIGS. 1 and 2). As the threaded cylindrical portion and therespective threaded bore may be larger than in that of the screw and therespective receiving thread of the prior art devices, the mechanicalconnection and consequently electrical connection between the threadedportions and the contact surfaces may also be of improved.

Electrical contact is established when the contact surfaces are inelectrical contact, but may additionally also be established when thelocking surfaces are in contact. For example, as the threadedcylindrical portion and the threaded bore can be relatively large, themechanical connection can be relatively strong and, as a consequence ofthe stronger mechanical connection and the larger area at which thethreaded portions contact, the electrical connection may be improvedcompared with prior art devices. In a specific embodiment the contactarea that is established when the locking surfaces are interlocked is atleast as large as the contact area that is established when the contactsurfaces are in contact.

Alternatively or additionally, a portion of one of the locking surfacesmay be arranged to scrape over a portion of the other locking surfacewhen the locking surfaces interlock.

The first contact surface may have a conical tip and the second contactsurface may have a respective conical bore arranged to receive theconical tip of the first contact surface. Alternatively, the firstcontact surface may have a conical bore and the second contact surfacemay have a respective conical tip arranged to be received by the conicalbore of the first contact surface.

The first and the second contact surfaces may have matching profiles.

The conical tip may have a surface that is not curved or that isoutwardly curved and arranged for contact with the conical bore within aring-like zone near the apex of the curvature. In this case the conicalbore may have a surface that is not curved or that has a suitableinwardly or outwardly curved profile. Alternatively, the conical tip mayhave a surface that is inwardly curved and that is arranged for contactwith a suitable inwardly or outwardly curved conical bore. For example,the inwardly or outwardly curved surfaces may have a curvature that hasa profile corresponding to a section of a sphere. Each curved surfacemay also comprise more than one curvatures.

For example, a portion of one of the contact surfaces may be arranged toscrape over a portion of the other contact surface when the lockingsurfaces interlock whereby the contact surfaces may be cleaned andseated onto each other and therefore a better electrical contact may beestablished.

The invention will be more fully understood from the followingdescription of specific embodiments. The description is provided withreference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a cross-sectional representation of an electrical connectorfor connecting a core of a machine cable to a socket of an electricalconnection device (prior art),

FIG. 2 shows a cross-sectional representation of another electricalconnector for connecting a core of a machine cable to a socket of anelectrical connection device (prior art),

FIG. 3 shows an electrical connector for connecting a core of a machinecable to a socket of an electrical connection device according to aspecific embodiment,

FIG. 4 shows an electrical connector for connecting a core of a machinecable to a socket of an electrical connection device according toanother specific embodiment,

FIG. 5 shows an electrical connector for connecting a core of a machinecable to a pin of an electrical connection device according to a furtherspecific embodiment, and

FIGS. 6 (a) and (b) show details of the electrical connector accordingto yet another specific embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 3, a plug incorporating an electrical connectoraccording to a specific embodiment is now described. The plug 28comprises a socket 32 and a thimble 31. In this embodiment, socket 32and thimble 31 are each integrally formed. The thimble 31 is connectedto a core 33 of a machine cable 37. The socket 32 is arranged to receivea pin (not shown) and has a threaded cylindrical portion that isinter-locked with a threaded bore of the thimble 31.

The plug 28 comprises a body 29 that is of substantially cylindricalshape and an outer shell 30 composed of metallic and/or insulatingmaterial(s). The plug 28 has an end-face 38 that has three aperturesthat are defined by nuts such as nuts 34 and 35. From each aperture aninsulating sleeve 36 projects inwardly. Thimble 31 has a key (not shown)and sleeve 36 has a corresponding key way (not shown) arranged so thatrotation of the thimble 31 in the sleeve 36 can be avoided wherebyscrewing of the socket 32 into the thimble 31 is simplified.Alternatively, the sleeve 36 may have a key and the thimble 31 may havea corresponding key way arranged so that rotation of the thimble 31 isavoided when the socket 32 is screwed into the thimble 31.

Referring now to FIG. 4, the electrical connection device 40 comprisinga socket 42 and a thimble 44 is described in more detail. The socket 42is arranged to receive a pin (not shown) and the thimble 44 comprises aplurality of recesses 45 arranged to be connected to individual branchesof a core of a machine cable (not shown). The socket 42 has a firstlocking surface which has the form of cylindrical portion 46 having anouter thread. The thimble 44 comprises a complimentary threaded bore 48arranged to receive the cylindrical threaded portion 46. The outerdiameter of the cylindrical threaded portion 46 is relatively largecompared with the outer diameter of the socket and it therefore ispossible to achieve a relative strong inter-locking of the threadedcylindrical portion with the threaded bore.

The socket 42 has a contact surface 50 and the thimble 44 has a matchingcontact surface 52. In this example the contact surface 50 is providedin form of a conical tip of the threaded cylindrical portion 46. Thethimble 44 has a respective conical extension which provides the contactsurface 52 arranged to be in electrical contact with the conical contactsurface 50. The contact surface 50 and the contact surface 52 havematching profiles.

FIG. 5 shows a variation 59 of the device shown in FIG. 4 comprising apin 60 instead of the socket in the device shown in FIG. 4. The pin 60is arranged to receive a socket (not shown) and is interlocked with thethimble 44 in the same way as the socket 42 shown in FIG. 4.

It will be appreciated that the socket 42 of the device 40 shown in FIG.4 and the pin 60 of the device 59 shown in FIG. 5 can be exchanged.Therefore, a connector such as a plug or receptacle incorporating device40 and/or 59 shown has the advantage of greater flexibility comparedwith prior art devices where pins and sockets are not exchangeable (seeFIGS. 1 and 2).

Referring now to FIG. 6 (a), the electrical connection device is nowdescribed in further detail. FIG. 6 (a) shows a portion of a socket 61and a portion of a thimble 62 interlocked with the socket 61. In thisembodiment, the socket 61 has a cylindrical portion 64 with outerthread. The cylindrical portion 64 has a conical tip 66 which provides acontact surface 68. The thimble 62 has a threaded bore 70 that has acontact surface 72 in form of a conical bore shaped complimentary to theconical tip 66 of the cylindrical portion 64. If the threadedcylindrical portion 64 is screwed into the threaded bore 70, the conicaltip 66 scrapes over the conical contact surface 72 when the socket 61 isinterlocked with the thimble 62 whereby the contact surfaces are cleanedand therefore a better electrical contact may be established.

Referring now to FIG. 6 (b), a variation of the electrical connectiondevice is now described. In this case the socket 80 has a conicalcontact surface 82 that is curved. The area in which electrical contactbetween the contact surface 82 and the contact surface 72 of the thimble62 is near within a ring-like zone near the apex of the curvature andmay be smaller than that of the device shown in FIG. 6 (a). However, thecurved conical contact surface profile 82 may have other advantages suchas a progressive cleaning action when the contact surfaces scrape evereach other when the thimble 62 and the socket 80 are being engagedtogether. Such scraping action may result in one contact surface beingseated on the other contact surface which would improve the electricalconnection as interfacial resistance can be reduced.

Although the invention has been described with reference to particularexamples, it will be appreciated by those skilled in the art that theinvention may be embodied in many other forms. For example, theconnector may comprise a pin instead of the socket as described in theabove embodiments. Also, the thimble may have a threaded cylindricalportion and the socket may have a threaded bore arranged to receive thethreaded cylindrical portion. Further, the socket and the thimble maynot be integrally formed but may be composed of different parts that arejoined.

The invention claimed is:
 1. An electrical connector arranged forconnecting a core of a machine cable to a pin or a socket of anelectrical connection device, the connector comprising: a first parthaving a first locking surface and having a further surface that forms afirst contact surface, the first part further including a pin or asocket which is electrically connected to the first contact surface, asecond part having a second locking surface arranged to interlock withthe first locking surface and having a further surface that forms asecond contact surface which is arranged to contact the first contactsurface, the second part further including a projection for securing thecore of the machine cable to the second part, the projection beingelectrically connected to the second contact surface, wherein the firstlocking surface comprises a first threaded portion and the secondlocking surface comprises a second threaded portion arranged to receivethe first threaded portion, and wherein the contact surfaces arearranged so that, when the locking surfaces are interlocked, the contactsurfaces are in electrical contact with each other so that an electricalcontact is established between the core of the machine cable and the pinor socket, wherein one of the first or the second contact surfaces has aconical tip and the other one of the first and second contact surfacehas a conical bore arranged to receive the conical tip, and wherein theconical tip comprises an outwardly curved surface which is arranged forcontact with the conical bore within a ring-like zone near the apex ofthe curvature, or the conical bore comprises an inwardly curved surfacewhich is arranged for contact with the conical tip within a ring-likezone near the apex of the curvature.
 2. The electrical connector asclaimed in claim 1 wherein the electrical connection device is arrangedfor delivery of a power of a few hundred kilowatts.
 3. The electricalconnector as claimed in claim 1 wherein the electrical connection deviceis arranged for delivery of power having an associated voltage of one ormore kilovolts.
 4. The electrical connector as claimed in claim 1wherein the first locking surface is positioned between the firstcontact surface and the pin or socket.
 5. The electrical connectiondevice as claimed in claim 1 wherein the second contact surface ispositioned between the second locking surface and the projection.
 6. Theelectrical connector as claimed in claim 1 wherein the first part hasopposing first and second end-portions, the first end-portion includinga socket and the second end-portions end portion including the firstcontact surface.
 7. The electrical connector as claimed in claim 6wherein the a second end-portion of the second part includes the secondlocking surface and the second end-portion of the first part includesthe first locking surface.
 8. The electrical connector as claimed inclaim 1 wherein the first part has opposing first and secondend-portions, the first end-portion including a pin and the secondend-portions end-portion including the first contact surface.
 9. Theelectrical connector as claimed in claim 8 wherein the a secondend-portion of the second part includes the second locking surface andthe second end-portion of the first part includes the first lockingsurface.
 10. The electrical connector as claimed in claim 1 wherein atleast one of the first part and the second part is integrally formed.11. The electrical connector as claimed claim 1 wherein a portion of oneof the contact surfaces is arranged to scrape over a portion of theother contact surface when the locking surfaces interlock.
 12. Theelectrical connector as claimed in claim 1 wherein a portion of one ofthe locking surfaces is arranged to scrape over a portion of the otherlocking surface when the locking surfaces interlock.
 13. The electricalconnector as claimed in claim 1 wherein the first threaded portion is acylindrical portion having an outer thread and the second threadedportion is a complimentary threaded bore arranged to receive thecylindrical portion.
 14. The electrical connector as claimed in claim 1wherein the second threaded portion is a cylindrical portion having anouter thread and the first threaded portion is a complimentary threadedbore arranged to receive the cylindrical portion.
 15. The electricalconnector as claimed in claim 1 wherein the second contact surface has aconical tip and the first contact surface has a respective conical borearranged to receive the conical tip of the second contact surface. 16.The electrical connector as claimed in claim 15 wherein the conical borecomprises an inwardly curved surface which is arranged for contact withthe conical tip within a ring-like zone near the apex of the curvature.17. The electrical connector as claimed in claim 1 wherein the firstcontact surface has a conical tip and the second contact surface has arespective conical bore arranged to receive the conical tip of the firstcontact surface.
 18. The electrical connector as claimed in claim 17wherein the conical tip comprises an outwardly curved surface which isarranged for contact with the conical bore within a ring-like zone nearthe apex of the curvature.
 19. The electrical connector as claimed inclaim 17 wherein the conical bore comprises an inwardly curved surfacewhich is arranged for contact with the conical tip within a ring-likezone near the apex of the curvature.
 20. The electrical connector asclaimed in claim 1 wherein the first and the second contact surfaceshave matching profiles.
 21. The electrical connector as claimed in claim20 wherein the conical tip comprises an outwardly curved surface whichis arranged for contact with the conical bore within a ring-like zonenear the apex of the curvature.